The 1-3-year-old bamboo (Phyllostachys puberscence) culms were exposed to ambient weathering conditions for 12 months. Changes in color, surface topography, and chemical features of bamboo culms by weathering were investigated. Changes in the surface color of culms increased sharply in the first 3 months weathering and then slowly decreased compared to control culms. Surface checks developed more markedly in the 2- and 3-year-old bamboos than in the 1-year-old ones. The depth of erosion was extended up to 150 A mu m from the outer surface of culms. Solid-state NMR (nuclear magnetic resonance) and FT-IR (Fourier transform infra-red) spectra showed that the lignin and hemicelluloses of bamboo culms were preferentially affected by natural weathering, while crystalline cellulose remained relatively intact.